Observations on the macula lutea / by George Lindsay Johnson.

  • George Lindsay Johnson
Date:
[1896]
Catalogue details

Licence: Public Domain Mark

Credit: Observations on the macula lutea / by George Lindsay Johnson. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    OBSERVATIONS ON THE MACULA LUTEA. By GEORGE LINDSAY JOHNSON, M.D. (Cantab.), F.R.C.S. (London). HISTOLOGY OF THE HUMAN MACULA {Continued). C.—THE MEMBRANA LIMITANS EXTERNA. rT^HE older writers describe the membrana limitans externa as a true membrane ; later authors consider it a fenestrated membrane ; my observations however tend to show that neither of these views is correct. No mem- brane separates the bacillary from the outer granular layer, but coarse fibres run parallel to the plane of the retina inter- twining with the basal portion of the rods and cones, just as the weft of a fabric interlaces the warp, forming a support- ing tissue for the bacillary layer. If we examine the vertical sections illustrated in Figs. 15 to 20 we find that in thin sections the membrana limitans externa appears as a straight rouletted line, which is the appearance that interlaced fibres have when viewed ver- tically, and this is confirmed by transverse sections as shown in Fig. 23, which is taken from a section only slightly oblique, so that three or four rows of these stout intertwin- ing fibres can be seen. The so-called membrana limitans externa is invariably a straight line when seen in vertical sections. Whenever it appears wavy it is due to shrinkage of the specimen. It is this straight line formed by the intertwining fibres which has hitherto been regarded as the section of a membrane. Transverse sections now show us the real structure. There are only two membranes in the retina, the membrana limi- tans interna and the membrana terminans, the latter contigu- Reprinted from the Archives of Ophthalmology, Vol. xxv., No. 4, 1896.